Xiao X. Wei

Sarcomatoid and rhabdoid (S/R) renal cell carcinoma (RCC) are highly aggressive tumors with limited molecular and clinical characterization. Emerging evidence suggests immune checkpoint inhibitors (ICI) are particularly effective for these tumors, although the biological basis for this property is largely unknown. Here, we evaluate multiple clinical trial and real-world cohorts of S/R RCC to characterize their molecular features, clinical outcomes, and immunologic characteristics. We find that S/R RCC tumors harbor distinctive molecular features that may account for their aggressive behavior, including BAP1 mutations, CDKN2A deletions, and increased expression of MYC transcriptional programs. We show that these tumors are highly responsive to ICI and that they exhibit an immune-inflamed phenotype characterized by immune activation, increased cytotoxic immune infiltration, upregulation of antigen presentation machinery genes, and PD-L1 expression. Our findings build on prior work and shed light on the molecular drivers of aggressivity and responsiveness to ICI of S/R RCC.

BACKGROUND: Tumor content in circulating cell-free DNA (cfDNA) is a promising biomarker, but longitudinal dynamics of tumor-derived and non-tumor-derived cfDNA through multiple courses of therapy have not been well described. METHODS: CfDNA from 663 plasma samples from 140 patients with castration-resistant prostate cancer (CRPC) was subject to sparse whole genome sequencing. Tumor fraction (TFx) estimated using the computational tool ichorCNA was correlated with clinical features and responses to therapy. RESULTS: TFx associated with the number of bone metastases (median TFx = 0.014 with no bone metastases, 0.047 with 1-3 bone metastases, 0.190 for 4+ bone metastases; P < 0.0001) and with visceral metastases (P < 0.0001). In multivariable analysis, TFx remained associated with metastasis location (P = 0.042); TFx was positively correlated with alkaline phosphatase (P = 0.0227) and negatively correlated with hemoglobin (Hgb) (P < 0.001), but it was not correlated with prostate specific antigen (PSA) (P = 0.75). Tumor-derived and non-tumor-derived cfDNA track together and do not increase with generalized tissue damage from chemotherapy or radiation at the time scales examined. All new treatments that led to ≥30% PSA decline at 6 weeks were associated with TFx decline when baseline TFx was >7%; however, TFx in patients being subsequently maintained on secondary hormonal therapy was quite dynamic. CONCLUSION: TFx correlates with clinical features associated with overall survival in CRPC, and TFx decline is a promising biomarker for initial therapeutic response. TRIAL REGISTRATION: Dana-Farber/Harvard Cancer Center (DF/HCC) protocol no. 18-135. FUNDING: Wong Family Award in Translational Oncology, Dana Farber Cancer Institute Medical Oncology grant, Gerstner Family Foundation, Janssen Pharmaceuticals Inc., and Koch Institute Support (core) grant P30-CA14051 from the National Cancer Institute (NCI).

PURPOSE In this multicenter phase II trial, we evaluated atezolizumab combined with bevacizumab in patients with advanced renal cell carcinoma (RCC) with variant histology or any RCC histology with ≥ 20% sarcomatoid differentiation. PATIENTS AND METHODS Eligible patients may have received previous systemic therapy, excluding prior bevacizumab or checkpoint inhibitors. Patients underwent a baseline biopsy and received atezolizumab 1,200 mg and bevacizumab 15 mg/kg intravenously every 3 weeks. The primary end point was overall response rate (ORR) by RECIST version 1.1. Additional end points were progression-free survival (PFS), toxicity, biomarkers of response as determined by programmed death-ligand 1 (PD-L1) status, and on-therapy quality-of-life (QOL) metrics using the Functional Assessment of Cancer Therapy Kidney Symptom Index-19 and the Brief Fatigue Inventory. RESULTS Sixty patients received at least 1 dose of either study agent; the majority (65%) were treatment naïve. The ORR for the overall population was 33% and 50% in patients with clear cell RCC with sarcomatoid differentiation and 26% in patients with variant histology RCC. Median PFS was 8.3 months (95% CI, 5.7 to 10.9 months). PD-L1 status was available for 36 patients; 15 (42%) had ≥ 1% expression on tumor cells. ORR in PD-L1–positive patients was 60% (n = 9) v 19% (n = 4) in PD-L1–negative patients. Eight patients (13%) developed treatment-related grade 3 toxicities. There were no treatment-related grade 4-5 toxicities. QOL was maintained throughout therapy. CONCLUSION In this study, atezolizumab and bevacizumab demonstrated safety and resulted in objective responses in patients with variant histology RCC or RCC with ≥ 20% sarcomatoid differentiation. This regimen warrants additional exploration in patients with rare RCC, particularly those with PD-L1–positive tumors.